.help onedspec (Oct84) "Spectral Reductions"
.ce
Relationship Between Onedspec and Twodspec
.ce
Discussion
.ce
October 24, 1984
.sp 3
Two types of interactions between one dimensional and two dimensional
spectra may be defined:

.ls (1)
Perform a one dimensional operation on the average or sum of a set
of lines in a two dimensional image.
.le
.ls (2)
Perform a one dimensional operation successively on a set of lines
in a two dimensional image.
.le

The two functions might be combined as:

.ls (3)
Perform a one dimensional operation on the average or sum of a set
of lines in a two dimensional image and apply the one dimensional
result successively on a set of lines in a two dimensional image.
.le

Examples of this are dispersion solutions and flux calibrations for
longslit spectra.

     Some choices for implementation are:

.ls (1)
Use a 2-D to 1-D operator to create a 1-D spectrum by averaging or summing
lines.
.le
.ls (2)
Use an apply a 1-D arithmetic correction to a 2-D image operator.
Alternatively, expand a 1-D correction to a 2-D correction.
.le
.ls (3)
Convert the 2-D image to a group of 1-D images and provide the 1-D operators
with the ability to perform averaging or summation.
.le
.ls (4)
To perform a one dimensional operation successively on
a set of lines first convert the two dimensional image into a group
of one dimensional spectra.  Perform the 1-D operation on the desired
elements of the group and then reconstruct the 2-D image from the group
of 1-D images.
.le
.ls (5)
Built separate operators for 2-D images using the 1-D subroutines.
.le
.ls (6)
Provide the ability in the 1-D operators to perform the desired 2-D
operations directly.
.le

     Options (1) and (2) are essentially what is done on the IPPS.  Option (5)
would lessen the amount of development but increase the number of tasks
to be written.  I find option (6) desirable because of its
increased generality but it would require a
further definition of the data structures allowed and the syntax.
.endhelp